Motor operated chuck for lathes and other machine tools



w. BERG 2,006,621

MOTOR OPERATED CHUCK FOR LATHES AND OTHER MACHINE TOOLS July 2, 1935.

Original Filed May 2, 1932 Patented July 2, 1935 UNITED STATES PAT ENT' OFFICETf DTHER; MACHINE TQOLS- -Wilhelin ner Bielefeld, Germany Original application May 2, 1932, Serial No. 608,763, now'Patent No. 1,971,638.. Divided and this application January 19,. 1934, Serial No. 707,363.. In Germany. September 4,. 1931 2Clairns. a msry The invention relates to a chuck for lathes and machine tools: inwhich the motor, for instancean electromotor, effects the adjusting of the clamping cheeks. In this arrangement the motor must be able to; continue'to; run after'the clamping proceeding has been terminated, that is when the clamping cheeks bear tightly against the work and can no longer move.

This application is a division of application Serial No. 608,763, filed May 2, 1932, now Patent No. 1,971,638.

The reason herefor is to avoid that the motor must be stopped at the moment when the clamping proceeding is terminated. This is attained in that between the motor and the shaft driving the clamping cheeks a gear is inserted which serves to reduce the high revolving speed of the motor shaft and which is further so arranged that the running of the motor can continue after the termination of the clamping proceeding without any separate manipulation being required. With this object in View a differential or planet gear of known type is employed, the base wheel of this gear being driven from the motor and a runner wheel being arranged at the side of said base wheel and gears with the driving shaft for the chuck. The runner wheel has a diiierent number of teeth than the base wheel.

The base wheel is fitted with a locking device constructed so that by the same also the limiting of the clamping pressure can be attained. The arrangement may consist for instance of spring controlled poles or looking bolts engaging from the inner side with notchesin the circumference of the base wheel.

If therefore the base wheel acted upon by the spring controlled locking element is stopped, the runner wheel rotates and effects the opening and closing of the chuck. If, however, the clamping is terminated, the runner wheel remains inoperative, Whereas the looking on the base wheel, that is the spring controlled locking bolts yield and the base wheel continues to rotate, the motor continuing to run.

The mechanical locking of the base wheel may be regulated in various manners. The number of spring controlled locking bolts may be changed or the spring pressure varied. In both cases it is possible to exert by mechanical means the quite determined clamping pressure. This arrange- -ment of the spring controlled locking bolt on the circumference of the base wheel presents, however, another advantage.

It is a well known phenomenon that the blank tends to turn in the clamping cheek during the working operation owing to the stressing. A; greater additional clamping pressure is thereby, produced than that which is appliedby motor on by hand to the. clamping cheeks. This: results, however, in that, when disengaging, the first. dis- 5 engaging pressure must be greater thanthe lest clampin pressure.

If therefore a mechanical regulating device were to be employed which does not take this circumstance into consideration the result would be 10 that, when disengaging, a suflicient disengaging pressure could not be transmitted for disengaging the clamping cheeks.

Consequently, locking bolts are arranged at certain distances apart around the circumfer- 15 ence of the base wheel so that, between the individual notches, the motor can run idle when the locking bolt is disengaged in order to thus accumulate energy in its rotating mass which, when the locking bolt suddenly engages in the base 20 wheel, is converted into a considerably increased turning moment. This sequence repeats itself until the disengagement has been efiected.

The minimum spacing of the notches in the circumference of the base wheel is therefore 25 determined by the idle running time of the motor, which is necessary for storing the energies required for disengaging the clamping cheeks.

An embodiment of the invention is illustrated by way of example on the accompanying drawing. 30

Fig. 1 shows in longitudinal section the chuck driven by an electric motor.

Fig. 2 is a cross section through the base wheel on line 2-2 of Fig. 1.

In the chuck body I the clamping device 2 for 35 the clamping checks 1 is arranged. This clamping device is driven from a shaft I2 on which a runner wheel II is keyed. At the side of this runner wheel a base wheel 10 of the planet gear is arranged. The two wheels have a slightly 40 diiferent number of teeth and the circulating planet wheels 8 mesh with the internal teeth of the said two wheels, said planet wheels 8 being driven by a pinion 6 from the shaft of an electromotor 9. On the circumference of the base wheel 45 locking bolts l3, preferably bevelled at the lower end, are arranged which are spring controlled, the spring pressure adapted to be altered by the adjusting of brushes l4. During the clamping proceeding the locking bolt securely holds the 0 base wheel In so that the runner wheel ll rotates. At the moment at which the clamping proceeding is terminated, the runner wheel H is stopped, whereas the clamping pressure of the locking bolts is overcome by the kinetic energy 55 of the motor so that the locking bolt disengages and the base wheel rotates.

It is a well known phenomenon that the blank tends to turn in the clamping chucks during the working operation owing to the stressing. A greater additional clampingpressure is thereby produced than that which is supplied by the motor or by hand 'into the clamping jaws. This results, however, in that when disengaging, the first disengaging pressure must be greater than the last clamping pressure. 7 I

It therefore a mechanical regulatingparrangement existed, which does not account for this circumstance, the result would be that when disengaging, a suflicient disengaging pressure could not be transmitted for disengaging the clamping cheeks. Consequently locking bolts are arranged at certain distances apart around the. circumierence of the base wheel so that between the individual notches the motor can run idle when the locking bolt is disengaged in order to thus accumulate energy in its rotating mass which, when the locking bolt suddenly engages in the base wheel, is shock-like converted into a considerably increased turning moment. This repeats itself until the disengagement has been effected. The minimum spacing of the notches coaxial and having a diflerent number of teeth to said base wheel, and common intermediate wheels adapted to drive both said base wheel and said runner wheel, variable spring loaded bolts arranged in the circumference of said casing and engaging in the notches of said base wheel and adapted to disengage only atv the termination of the clamping operation whilst the driving motor is still running.

2. A motor actuated chuck as specified in claim 1, in which the minimum spacing of the notches around the periphery of the base wheel for en-' gaging the locking bolts is such that the idle running time of the motor between two positions is suflicient toaccumulate the energy for disengaging the chuck.

. WILHELM BERG. 

